Obesity is one of risk factors of various diseases such as arteriosclerosis. Therefore, it is strongly required to inhibit, ameliorate or prevent obesity. Obesity is a state where excess lipid is stored in the body. One of causes for lipid storage in the body includes, for example, excess ingestion of carbohydrate. When ingested in the body, carbohydrate contained in food products and beverages is generally digested by a digestive enzyme to exclusively form a monosaccharide, which is absorbed into the body through the enteric canal. The monosaccharide is converted into lipid in the lipid cells to form an adipose tissue. It is considered that various pathologies are caused by intraperitoneal storage of visceral lipid among these adipose tissues.
In case a large amount of saccharides such as fructose are ingested in the form of sucrose, portion of the saccharides promotes the synthesis of fatty acid in the liver and also enhaces the esterification of fatty acid. As a result, a large amount of triglyceride (triacyl glycerol, neutral lipid) is produced.
The liver converts triglyceride into a very low-density lipoprotein (VLDL) and secretes it in blood serum. In that case, when a large amount of triglyceride is produced, an ability capable of producing lipoprotein of the liver does not follow so that triglyceride is stored in the liver and fatty liver progresses, thus entering into cirrhosis soon.
An increase in secretion of VLDL causes hyperlipemia. Hyperlipemia is also caused by a reduction in insulin sensitivity (insulin resistance) due to excess ingestion of carbohydrate and deteriorates disease conditions. An increase in VLDL concentration in blood is also a major cause for arteriosclerosis. Arteriosclerosis causes thrombosis and is also one of factors for various circulatory system diseases such as cerebral infarction and cardiac infraction.
As described above, excess ingestion of saccharides causes obesity, thus causing various diseases. Therefore, there has hitherto been developed an anti-obestic agent, which can inhibit, ameliorate or prevent obesity by inhibiting any pathway leading to obesity.
Typical anti-obestic agent includes a carbohydrate digestive enzyme inhibitor, and an α-glucosidase inhibitor, for example, “Acarbose” (manufactured by Bayer Yakuhin, LTD.) has widely been used as a drug.
However, since a conventional anti-obestic agent is a chemically synthesized product, users feel uneasy in view of safety on administration. It could not sufficiently respond to requirements for inhibition or amelioration of obesity in a dairy life. It is particularly advantageous for inhibition, amelioration and prevention of obesity if an anti-obestic action can be imparted to food products and beverages, which are ordinarily ingested.
Therefore, various anti-obestic agents derived from natural substances such as plant have been suggested. For example, diet food products and beverages, containing an extract of Gymnema Indorum as a plant native to India is described in Unexamined Patent Publication (Kokai) No. Hei 5-252897. A weight control agent containing an oolong tea saponin and an oolong tea fiber is described in Unexamined Patent Publication (Kokai) No. Hei 9-227996. A carbohydrate digestive enzyme inhibitor containing an extract of Ephedra Herb used as a Chinese herbal remedy is described in Unexamined Patent Publication (Kokai) No. Hei 9-2963. An anti-obestic agent containing a seed coat extract of Tamarindus indica L. of the legminous family as an active ingredient is described in Unexamined Patent Publication (Kokai) No. Hei 9-291039.
However, an anti-obestic agent having a safe and higher anti-obestic action has been required. Furthermore, there has also been required an active ingredient derived from natural substances, which is also superior in action of inhibiting lipid storage, action of reducing a concentration of triglyceride and action of reducing a concentration of cholesterol in blood.